Eye-tracking enabled wearable devices

ABSTRACT

A system for determining a gaze direction of a user is disclosed. The system may include a first illuminator, a first profile sensor, and at least one processor. The first illuminator may be configured to illuminate an eye of a user. The first profile sensor may be configured to detect light reflected by the eye of the user. The processor(s) may be configured to determine a gaze direction of the user based at least in part on light detected by the first profile sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Provisional U.S. Patent ApplicationNo. 62/329,719 filed Apr. 29, 2016, entitled “WEARABLE DEVICE COMPRISINGA DISPLAY AND IMAGE SENSOR,” as well as Provisional U.S. PatentApplication No. 62/232,268 filed Sep. 24, 2015, entitled “WEARABLEDEVICE COMPRISING A DISPLAY AND IMAGE SENSOR,” the entire disclosures ofwhich are hereby incorporated by reference, for all purposes, as iffully set forth herein.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a system for determining a gaze direction of a useris provided. The system may include a first illuminator, a first profilesensor, and at least one processor. The first illuminator may beconfigured to illuminate an eye of a user. The first profile sensor maybe configured to detect light reflected by the eye of the user. Theprocessor(s) may be configured to determine a gaze direction of the userbased at least in part on light detected by the first profile sensor.

In another embodiment, a method for determining a gaze direction of auser is provided. The method may include illuminating an eye of a user.The method may also include detecting, with a profile sensor, lightreflected by the eye of the user. The method may further includedetermining, with at least one processor, a gaze direction of the userbased at least in part on light detected by the profile sensor.

In another embodiment, a non-transitory machine readable medium havinginstructions stored thereon for determining a gaze direction of a useris provided. The instructions may be executable by one or moreprocessors to perform a method. The method may include causing anilluminator to illuminate an eye of a user. The method may also includedetecting, with a profile sensor, light reflected by the eye of theuser. The method may further include determining a gaze direction of theuser based at least in part on light detected by the profile sensor.

In another embodiment, a system for determining a gaze direction of auser is provided. The system may include a first illuminator, an areaimage sensor, and at least one processor. The first illuminator may beconfigured to illuminate an eye of a user. The area image sensor may beconfigured to detect light reflected by the eye of the user. The atleast one processor may be configured to determine a gaze direction ofthe user based at least in part on light detected by the area imagesensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in conjunction with the appendedfigures:

FIG. 1 shows an exemplary wearable device of the invention having adisplay device and an eye tracking device;

FIG. 2 shows an exemplary profile sensor output of various embodimentsof the invention;

FIG. 3A shows horizontal and vertical pixel binning used in variousembodiments of the invention;

FIG. 3B shows one possible method embodiment of the invention fordetermining gaze direction;

FIG. 4 shows one embodiment of the invention where a cold mirror isapplied to a headset lens;

FIG. 5 shows one possible method embodiment of the invention for panningof a virtual reality display;

FIG. 6 shows one possible method embodiment of the invention for mappinginput devices to virtual objects;

FIG. 7A shows one system embodiment of the invention forsensor/illuminator arrays disposed on and/or in a lens of a wearabledevice;

FIG. 7B shows a close-up view of one embodiment of the invention whereoptical fibers are disposed within grooves on a primary viewing lens;

FIG. 7C shows a profile view of a termination point of the optical fiberof FIG. 7B;

FIG. 8 is a block diagram of an exemplary computer system capable ofbeing used in at least some portion of the apparatuses or systems of thepresent invention, or implementing at least some portion of the methodsof the present invention;

FIG. 9 is s a view of a display device of the invention in which imagemodification is occurring in response to a user's gaze point;

FIG. 10A is a diagram of how image quality may continuously vary withina modified image area;

FIG. 10B is a diagram of how image quality may vary in steps within amodified image area;

FIG. 11 is a view of a display device of the invention in which imagemodification is occurring in response to a detected change in a user'sgaze point; and

FIG. 12 is flow diagram of one possible method of the invention formodifying an image based on a user's gaze point.

In the appended figures, similar components and/or features may have thesame numerical reference label. Further, various components of the sametype may be distinguished by following the reference label by a letterthat distinguishes among the similar components and/or features. If onlythe first numerical reference label is used in the specification, thedescription is applicable to any one of the similar components and/orfeatures having the same first numerical reference label irrespective ofthe letter suffix.

DETAILED DESCRIPTION OF THE INVENTION

The ensuing description provides exemplary embodiments only, and is notintended to limit the scope, applicability or configuration of thedisclosure. Rather, the ensuing description of the exemplary embodimentswill provide those skilled in the art with an enabling description forimplementing one or more exemplary embodiments. It being understood thatvarious changes may be made in the function and arrangement of elementswithout departing from the spirit and scope of the invention as setforth in the appended claims.

For example, any detail discussed with regard to one embodiment may ormay not be present in all contemplated versions of that embodiment.Likewise, any detail discussed with regard to one embodiment may or maynot be present in all contemplated versions of other embodimentsdiscussed herein. Finally, the absence of discussion of any detail withregard to embodiment herein shall be an implicit recognition that suchdetail may or may not be present in any version of any embodimentdiscussed herein.

Specific details are given in the following description to provide athorough understanding of the embodiments. However, it will beunderstood by one of ordinary skill in the art that the embodiments maybe practiced without these specific details. For example, circuits,systems, networks, processes, and other elements in the invention may beshown as components in block diagram form in order not to obscure theembodiments in unnecessary detail. In other instances, well-knowncircuits, processes, algorithms, structures, and techniques may be shownwithout unnecessary detail in order to avoid obscuring the embodiments.

Also, it is noted that individual embodiments may be described as aprocess which is depicted as a flowchart, a flow diagram, a data flowdiagram, a structure diagram, or a block diagram. Although a flowchartmay describe the operations as a sequential process, many of theoperations can be performed in parallel or concurrently. In addition,the order of the operations may be re-arranged. A process may beterminated when its operations are completed, but could have additionalsteps not discussed or included in a figure. Furthermore, not alloperations in any particularly described process may occur in allembodiments. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc. When a process correspondsto a function, its termination corresponds to a return of the functionto the calling function or the main function.

The term “machine-readable medium” includes, but is not limited totransitory and non-transitory, portable or fixed storage devices,optical storage devices, wireless channels and various other mediumscapable of storing, containing or carrying instruction(s) and/or data. Acode segment or machine-executable instructions may represent aprocedure, a function, a subprogram, a program, a routine, a subroutine,a module, a software package, a class, or any combination ofinstructions, data structures, or program statements. A code segment maybe coupled to another code segment or a hardware circuit by passingand/or receiving information, data, arguments, parameters, or memorycontents. Information, arguments, parameters, data, etc. may be passed,forwarded, or transmitted via any suitable means including memorysharing, message passing, token passing, network transmission, etc.

Furthermore, embodiments of the invention may be implemented, at leastin part, either manually or automatically. Manual or automaticimplementations may be executed, or at least assisted, through the useof machines, hardware, software, firmware, middleware, microcode,hardware description languages, or any combination thereof. Whenimplemented in software, firmware, middleware or microcode, the programcode or code segments to perform the necessary tasks may be stored in amachine readable medium. A processor(s) may perform the necessary tasks.

The present invention generally relates to a wearable device including adisplay and an image sensor, the wearable device uses informationobtained through the image sensor to alter information on the display.In particular the present invention relates to systems and methods forutilizing information regarding an eye in altering information on adisplay.

Wearable devices containing displays are well known, typically they areutilized in Virtual Reality (VR) and Augmented Reality (AR) systems. Inthese systems the displays are used to provide a user with an experiencethat simulates either a different reality in the case of VR, or anenhanced reality in the case of AR.

In some cases the wearable device need not contain a display of anysort. For example a system described by U.S. Pat. No. 9,041,787 does notrequire a display. The entire contents of the aforementioned patent arehereby incorporated by reference, for all purposes, as if fully setforth herein.

In some embodiments, the use of eye tracking devices and the like can beincorporated with these wearable devices in order to improve theirperformance. For example, U.S. Patent Application Publication Number2015/0062322 describes a wearable eye tracking device. The entirecontents of the aforementioned patent publication are herebyincorporated by reference, for all purposes, as if fully set forthherein.

One implementation of eye tracking in a virtual reality device isdescribed in Using an Eye-Tracking System to Improve Camera Motions andDepth-of-Field Blur Effects in Virtual Environments, Hillaire et al,2008, Virtual Reality Conference, whereby eye tracking is used todetermine a user's focus point in a virtual embodiment. The focus pointis then used when rendering the virtual environment in order to improvethe user's sensation when navigating the virtual environment. The entirecontents of the aforementioned publication are hereby incorporated byreference, for all purposes, as if fully set forth herein.

Embodiments of the present invention seeks to provide improved solutionsfor eye tracking in wearable devices, and improved uses of eye trackinginformation in VR, AR, or other environments. These improvements mayrelate to hardware solutions for use in wearable devices, as well assoftware solutions for use with the same or similar devices.

Thus, an object of at least some embodiments of the present invention isto provide improved wearable eye tracking systems. This and otherobjects of embodiments of the present invention will be made apparentfrom the specification and claims together with appended drawings.

Various embodiments and aspects of the present invention will bearranged using headings herein, so as to facilitate more easyunderstanding of the present invention.

According to a first aspect of the present invention, there is provideda wearable device including at least a display and an eye trackingapparatus. Information from the eye tracking apparatus may be used by anassociated computing device (for example, computer, tablet, mobiledevice, or other processor enabled device) to influence or alter itemsdisplayed on the display.

In some embodiments, the eye tracking apparatus includes at least oneimage sensor and at least one illumination source. In some embodimentsthe eye tracking apparatus may include two image sensors and twoillumination sources. Any number of image sensors and illuminationssources are possible depending on the embodiment, and there may or maynot be an equivalent number of image sensors and illumination sources.The illumination sources project illumination onto the eye(s) of awearer of the wearable device, and the image sensor captures one or moreimages of the wearer's eye(s). Based on the location of reflection ofillumination on the eye, a direction of the user's gaze may bedetermined. By way of example, a suitable system for determining thegaze direction of a user with a wearable eye tracking apparatus isdescribed in U.S. Patent Application Publication Number 2015/0061996.The entire contents of the aforementioned publication are herebyincorporated by reference, for all purposes, as if fully set forthherein.

Connected directly or wirelessly to the eye tracking apparatus anddisplay may be a computing unit or other associated processing device.The computing unit, or other processing device, performs calculationsbased on information from the eye tracking apparatus and controlsinformation or other content displayed on the display, potentially aftertaking the calculations into account to modify the information or othercontent displayed on the display.

FIG. 1 shows a block diagram of a typical VR headset 100 with gazetracking of various embodiments of the invention. Different embodimentsof the invention may have fewer or greater number of components, and maybe located/configured variably, as discussed herein. Headset 100 mayinclude a display device 110, an eye tracking device 120 which includesilluminator(s) 123 and image/light sensor(s) 126. Illuminators 123 andimage/light sensors 126 may include dedicated lenses. Processor 130 mayprovide computational/operational control for the components. In someembodiments, headset 100 may also include a motion/movement detectionsubsystem 140 do detect movement of headset 100. A communication bus,not shown, may provide for wired and/or wireless communication with anassociated computing device.

Profile Sensor

In some embodiments, a profile sensor may be used to determine the gazedirection of a user. In these embodiments, a wearable device may beprovided which include at least one profile sensor directed towards atleast one of a user's eyes. An example of a suitable profile sensor isthat manufactured by Hammamatsu with model number S9132. A profilesensor operates by summarizing the values of all pixels in a row and/ora column into a single value, as will be understood by one of skill inthe art.

In addition, at least one infrared light emitter may be provided anddirected towards the at least one of the user's eyes. In this manner, aprofile sensor may be used to determine the location of a reflection ofthe infrared light from the user's cornea, otherwise referred to as a“glint.” Rudimentary gaze tracking may thus be performed by analyzingthe location of the glint on the user's cornea, as would be readilyunderstood by one of skill in the art. In a further improvement, two ormore profile sensors may be used. This offers several advantages.

First, if more than one two-dimensional profile sensor are used, it maybe possible to determine the cornea center of a user's eye inthree-dimensions, after determining the corneal radius and glintpositions in three dimensions, as opposed to two dimensions.

Secondly, arranging at least two profile sensors such that resultingglints do not overlap allows for more accurate glint detection. Forexample consider a case with two glints cause by illuminators A and B.If they are imaged by a one-dimensional profile sensor aligned in thesame direction as the glints, the sensor would only register a singleresponse caused by both glints, so it would be difficult or impossibleto determine whether the glint is caused by illuminator A, illuminatorB, or both. Aligning the illuminators and profile sensors in such a wayso that glints do not overlap in any readout of any profile sensor istherefore advantageous.

Alternatively, illuminators may be modulated to ensure that only oneilluminator is lit at any given time. A profile sensor in such anarrangement may be designed to operate at very fast sampling rate,enabling many samples, and capturing a glint from only one illuminatorat each sample within a short time frame to ensure only minimal eyemovement between samples.

Thirdly, multiple one-dimensional profile sensors may be used. In orderfor such a system to function accurately each sensor must be placed androtated relative to each other. In this manner the single dimension foreach sensor could be alternated between being in horizontal and verticalconfiguration, although the relative orientation difference need not belimited to 90 degrees. Furthermore it may be desirable in thesearrangements to add a cylindrical shaped lens to each one dimensionprofile sensor.

In some embodiments, the profile sensor may output the sum of all rowsand/or the sum of all columns of the pixel matrix of the sensor to aprocessing device. A reflection of infrared light from the infraredilluminator on a user's cornea, known as a glint, may be found using atechnique known as peak detection. Peak detection may be performed onboth the sum of the rows and the sum of the columns. FIG. 2 illustratesthis technique on an output of the sum of rows or columns, where thex-axis represents the pixels of the profile sensor, and the y-axisrepresents the magnitude, with an example of a peak highlighted.

In an optional improvement, in order to facilitate high speed eyetracking, where a previously calculated glint position is known—only asubset of pixels must be analyzed for a peak. For example, only 10-20pixels close to the known previous glint position may be analyzed.

Once the glint position is known, gaze direction can be determinedusing, for example, a polynomial glint to gaze point model:

gaze_(x) =c ₁ x+c ₂ y+c ₃ xy+c ₄ x ² +c ₅ y ² +c ₆

gaze_(y) =c ₇ x+c ₈ y+c ₉ xy+c ₁₀ x ² +c ₁₁ y ² +c ₁₂,

where gaze_(r) and gaze_(y) are the x and y positions of the gaze point,x and y are the x and y positions of the glint, and c1 . . . c12 arecalibrated model parameters.

In some embodiments, more than one illuminator may be provided incombination with the profile sensor. These illuminators may beselectively enabled or modulated, and the processing device maydetermine which illuminator to enable based on metrics derived fromcaptured image data. Alternatively, the illuminators may be lit in apredefined sequence ensuring that only one illuminator is lit at anygiven time.

In another embodiment, the wearable device further may contain at leastone image sensor of the conventional area sensor type. This conventionalsensor may also be directed to at least one of the user's eyes. Theconventional sensor may capture images of a user's eye and the systemmay perform traditional Pupil Centre Corneal Reflection (PCCR) eyetracking. PCCR is a well-known and readily understood method ofdetermining a user's gaze. Further information on this method can befound in multiple places, including Guestrin, E. D., Eizenman, E.,“General theory of remote gaze estimation using the pupil center andcorneal reflections,” Biomedical Engineering, IEEE Transactions, vol.53, no. 6, pp. 1124, 1133, June 2006.

By combining a profile sensor, enabled to output the sum of all columnsand/or the sum of all rows, with a conventional image sensor, the systemmay conduct glint tracking using the profile sensor, and PCCR trackingusing the conventional sensor. Due to the additional informationprovided by the profile sensor, the conventional sensor then need onlyrun at 0.5 to 10.0 Hz. Thus the system may achieve low powerconsumption, low latency, and a high frame (or sampling) rate.

A profile sensor tracking the glint will give sufficient gaze data aslong as the sensor stays fixed relative to the face of the user, whilethe images from the conventional image sensor allow for slippagecompensation whenever the sensor moves relative to the face. However, ingeneral, eye movements are substantially faster than any potentialslippage of a wearable device on the head of the user. So it istherefore of interest to find a way of only tracking the glint positionat low power and low latency. This may allow for foveated rendering inVR headsets where a relatively low power eye tracking solution can allowfor substantial savings in overall power consumption of the VR system,since graphics rendering power requirements can be significantlylowered.

For example, it may be possible to set the sensor in a mode where itcycles through two or more illuminators, having only one illuminator litper sensor exposure. For example, the sensor may be set to run in acycle where a first illuminator is lit during a first sensor exposureand then the sum of at least 10% of the pixel elements in at least 10%of the rows of the sensitive area and the sum of at least 10% of thepixel elements in at least 10% of the columns of the sensitive area arecalculated (and a glint position is detected). Thereafter, a secondilluminator is lit during a second sensor exposure and then the sum ofat least 10% of the pixel elements in at least 10% of the rows of thesensitive area and the sum of at least 10% of the pixel elements in atleast 10% of the columns of the sensitive area are calculated.Thereafter, the sensor captures a conventional image from at least a subpart of the sensitive area of the sensor while at least one of theilluminators is lit.

In an alternative implementation, the sensor may be set to run in acycle where a first illuminator is lit during a first sensor exposureand then the sum of at least 10% of the pixel elements in at least 10%of the rows of the sensitive area are calculated. Secondly the firstilluminator is lit during a second sensor exposure and the sum of atleast 10% of the pixel elements in at least 10% of the columns of thesensitive area calculated. Thereafter, the sensor captures aconventional image from at least a sub part of the sensitive area of thesensor while at least one of the illuminators is lit.

An image sensor enabled to operate as a conventional image sensor, butalso enabled to output profiles for the sum of pixel lines and/or thesum of pixel columns of the sensitive area, may include output pins forsynchronizing the exposure of one or multiple illuminators with thesensor exposure.

An image sensor enabled to operate as a conventional image sensor, butalso enabled to output profiles for the sum of pixel lines and/or thesum of pixel columns of the sensitive area, may also support daisychaining, thus allowing two or more sensors to connect to a processingunit through the same data bus, for example, a MIPI CSI-2 interface.

An image sensor enabled to operate as a conventional image sensor, butalso enabled to output profiles for the sum of pixel lines and/or thesum of pixel columns of the sensitive area, may further include meansfor detecting the distance to an object in its field of view. This maybe done through “time-of-flight” analysis.

To compensate for ambient light profile data and/or conventional imagedata, an image sensor may from time to time be sampled without activeillumination, i.e. without having any of the illuminators lit.

The image sensor may also be used to also identify the user for login,security, and/or other reasons through iris recognition.

An image sensor enabled to operate as a conventional image sensor, butalso enabled to output profiles for the sum of pixel lines and/or thesum of pixel columns of the sensitive area may also be designed so thatthat each pixel can only be included in the sum of columns or the sum oflines when the sensor is operated in profile mode. For example, thepixel elements may be laid out in a checker pattern where only everyother pixel may be summed into a row profile and the other pixels may besummed into a column profile.

An alternative implementation of the image sensor is to have thesensitive area split into a checker pattern where every other pixel isread out in rows and every other pixel is read out in columns,essentially having an AD converter next to each row, and an AD converternext to each column. This means that the conventional image for thissensor would be two images at half the sensor resolution, one read outvertically and one read out horizontally. This adds computationalcomplexity for the traditional PCCR eye tracking. FIG. 3 demonstratessuch a configuration in one example, as well as others discussed above,where an area image sensor emulating a profile sensor via its individualpixels, a 2D profile sensor, and/or two 1D profile sensors orientatedorthogonally, can be employed in a manner whereby every other pixel ofevery other row (as marked with ‘X’) is used for horizontal glint/imagedata acquisition (horizontal bins 1-5), and every other pixel of everyother column (also as marked with ‘X’) is used for vertical glint/imagedata acquisition (vertical bins 1-5).

The benefit would be that the sensor could be designed in such a waythat it supports horizontal pixel binning for the image read out fromeach line and vertical pixel binning for the image read out from eachcolumn, thus facilitation low power glint detection. For example, thesensor could be designed to sum of the values from 8-16 pixel elementsor even more into one value, meaning that it could operate as a profilesensor supporting sub-windowing functionality, which may facilitatesuppression of irrelevant signals and lower noise.

A sensor enabled to operate as a profile sensor, with or without supportfor sub-windowing, may include HW logic for detecting the center of theglint, thereby further reducing power consumption and the amount of datarequired to send to an external processing unit. In the case that thesensor supports sub-windowing the sensor may change the sub-windowposition, after glint center detection, to ensure that a followingprofile image includes the glint.

An alternative implementation of an eye tracker supporting bothtraditional PCCR eye tracking, as well as glint tracking, to allow forlow power eye tracking at latency and data rates supporting foveatedrendering, is to have a regular sensor for imaging of the eye, butinclude HW logic for glint center detection when the senor operates in acertain predefined sub-window mode. This may for instance only bepossible with a sub-window of 24×24 pixels, 32×32 pixels, 48×24 pixels,or some other appropriate resolution.

In some embodiments, organic light emitting diode (OLED) displays may beemployed. OLED displays are usually transparent, with a mirror placedbehind them to ensure that all light is sent out forward, toward theviewer. For eye tracking purposes, a cold mirror may be located behindan OLED display essentially reflecting all visible light from thedisplay towards the eye of the user but, letting through NIR light. Inthis manner, an eye tracking sensor detecting NIR light may be placedbehind the display, looking through it, toward the viewer, therebyrealizing an advantageous view angle towards the eye of the user.

In VR headsets it is also common to use Fresnel lenses to make thedisplay appear at further distance from the user than it really is. Thedrawback of having a lens like this is that it distorts the image fromthe display and likewise it will distort the image of the eye as seenfrom an eye tracking sensor looking through the lens. It may thereforebe preferable to compensate for this distortion in the eye trackingalgorithms.

An additional effect of the Fresnel lens is that it may cause circulardefects in the image of the eye, as seen from the eye tracking sensor.The pattern is similar to the distorting effect of waves on water whenyou throw in a small stone and try to look at something below thesurface. It may therefore be preferable to calibrate an eye trackingsensor viewing an eye through a Fresnel lens to ensure that the imagesfrom the sensor are adjusted to compensate for the defects of theFresnel lens, before machine vision algorithms try to detect differenteye features or glints.

An image sensor enabled to operate as a conventional image sensor, butalso enabled to output profiles for the sum of pixel lines and/or thesum of pixel columns of the sensitive area, may be designed to supportsub-windowing. This is common in conventional image sensors, but byallowing sub-windowing when operated in profile mode, much of thepotentially disrupting reflections or light sources in the field of viewfrom the sensor may be removed before the pixel elements are summed upto a row profile and/or column profile, thus ensuring higher accuracy inthe glint position determination, and allowing for re-centering of thesub-window for subsequent sample.

FIG. 3B shows a block diagram of possible methods 300 described abovefor determining a gaze direction of a user. At block 310, one or moreeyes are illuminated with one or more of the available illuminators. Atblock 320, one or more eyes are imaged via one or more of the availablesensors (profile sensors and/or area image sensors). Blocks 310 and 320may repeat as necessary. At block 330, as described above, the number ofsensors and/or what portion thereof, may be limited to focus on asub-window of likely pixels/resolution where imaging is likely necessaryto determine gaze location. Blocks 310, 320, and 330 may repeat asnecessary. At block 340, gaze direction may be determined, and blocks310, 320, 330, and 340 may repeat as necessary to continuallyre-determine changing gaze direction and/or sub-windowing as necessary.

Hot Mirror

In one embodiment, as shown in FIG. 4, a lens 400 is provided in awearable device such as a virtual reality headset. The lens 400 ispositioned such that a wearer of the device may view a display 110through the lens 400. Fixed atop the lens 400 is a hot mirror coating orfilm 410, and fixed atop the hot mirror film 410 are multipleilluminators 420. The film 410 has a cut-out portion 430 towards thecenter of the lens 400 to allow an eye tracking camera to view throughthe lens 400.

The hot mirror coating or film 410 may be applied directly onto the lens400, or for ease of manufacturing, the hot mirror coating or film 410may also be in the form of a separate piece which does not function as alens. Further, and also for ease of manufacturing, a separate piece ofglass or plastic may be placed atop the hot mirror, and the illuminators420 may be affixed to this separate piece.

The illuminators 420 may emit infrared light outwardly towards the eyeof a wearer 440, and then reflected by the eye of the wearer backtowards the lens 400. The film 410 has the properties of a hot mirror,in other words the film 410 allows light in the visible spectrum to passwhile preventing light in the infrared spectrum from passing. In thisway, visible light emitted by a display 110 behind the lens 400 may passto the wearer's eye, while most infrared light is prevented frompassing.

An image sensor located behind the lens, and looking through the cut-outportion 430, captures images of the wearer's eye containing reflectionsof the infrared light emitted by the illuminators 420, a processingdevice connected to the image sensor then analyzes those images todetermine a direction of the gaze of the user based on the reflectionsof the infrared light.

Although this embodiment has been described with reference to multipleinfrared illuminators 420, it is possible for the invention to functionadequately with only one illuminator.

Illuminators 420 may be applied to the film 410 in multiple ways,firstly simply through glue or alternatively a possible application isby printing electronics directly onto the film 410. The illuminators 420will further have to have communication lines applied to the film 410such that the illuminators may receive power so as to be turned on andoff.

In one embodiment, the wearable device includes two lenses 400 withassociated film 410 and illuminators 420. The film 410 may be applied tothe lens through glue or some other semi-permanent substance. In asystem with two lenses, light may reflect from the skin of a user intothe lenses, whereby the lenses have a waveguide effect and channel thelight away from the wearable device. The presence of the hot mirror 410acts to lessen the emergence of this light.

In an alternative embodiment, the illuminators 420 may be placed on theside of the lens 400 (or additional pieces as previously described).Illumination from the illuminators 420 may then travel through the lens400 to be emitted in front of the users eyes. This guiding of the lightoccurs in an area of the lens where the hot mirror 410 has been applied,so as to prevent illumination from being emitted towards the display110.

In a further addition to the present invention, an angled hot mirror 410may be added in front of the display 110, and the image sensor arrangedto view the hot mirror. The lens 400 is then placed in front of a user'seye with illuminators 420 located adjacent thereto. The illuminators 420illuminate the user's eye, and due to the lens 400 having a hot mirrorfilm or coating, as has been previously described, stray illuminationfrom the illuminators 420 is lessened. A cutout in the hot mirror filmor coating allows the image sensor is able to capture images of theuser's eye through the angled hot mirror.

Algorithms

In various embodiments, algorithms are used to determine, from an imagecontaining an eye and reflections of infrared light from said eye, agaze direction of the eye. A processing unit performs calculations basedon algorithms using captured images to determine the gaze direction.

Algorithms used in wearable devices described herein are substantiallysimilar to algorithms used in remote, existing eye tracking units. Assuch the fundamental approach to determining a gaze direction should bewell understood by a person of skill in the art.

However, several improvements are discussed below.

Pupil Position

One step in determining a gaze direction in an eye tracking device isestimating the pupil's position and size. In some embodiments, thefollowing method may be used to estimate pupil size and/or position.

In a captured image, the locations of reflections of the infrared lightemitted by illuminators are analyzed to determine their locationrelative to a previous captured image. The displacements of thereflections, in combination with the pupil's position from a previouscaptured image, are next used to determine the pupil's position in thecurrent image.

Fresnel Lens

When a Fresnel lens is present in a wearable device, an image capturedby the eye tracking image sensor through the Fresnel lens typicallycontains concentric circles as are present in the Fresnel lens. Theseconcentric circles can be mistakenly determined as pupil edges by theprocessing unit when attempting to determine gaze detection, thereforeit is necessary to quickly and accurately remove these concentriccircles.

In some embodiments, these concentric circles are removed from acaptured image using erosion. Erosion is an image processing conceptthat would be well understood by a person of skill in the art. Usingerosion, a small kernel, for example 3×3 or 5×5 pixels, is passed overthe captured image pixel by pixel. For each pixel, the intensity valueis replaced with the darkest pixel in the neighborhood of the pixel,where the neighborhood size is defined by the kernel. As the pupil in acaptured image is dark, the light concentric circles in the capturedimage are therefore replaced by the dark pupil.

Masking Light

Another embodiment, allows for the use of hardware or software toperform mathematical operations along lines across a 2D image sensor toprovide output similar to that of a profile sensor. The lines maytypically be the rows and columns of that sensor, but won't necessarilybe limited to these orientations. This would allow other operations thanjust the mean and/or sum of all pixel values on a line to be calculated,as well as making it possible to mask light contribution from parts ofthe image known not to contain any glints. Masking light contributionfrom parts of the image not containing any glints increases the signalto noise ratio, and hence aids in detection of the glint by allowingexamination of the intensity profile of a profile response. In exemplaryembodiments, the area to mask may be everything outside the cornea, andthe most recent output from the eye tracking algorithms could be used togive an approximate area to mask.

Simulating a 2D profile sensor using a traditional image sensor reducesthe computational load required for eye tracking and hence powerconsumption. However, framerate is limited to the framerate of the 2Dimaging sensors.

It is possible to mask light contribution from parts of the image notcontaining any glints even when using a real profile sensor.

One method to mask light from parts of the image known not to containany glints is through the use of one or several illuminators whose lightcan be spatially controlled (such as an infrared OLED array behind alens, any arrangement with a DLP or LCOS projector, or a multitude ofother solutions readily understood by one skilled in the art).

Yet another way to mask light from parts of the image known not tocontain any glints is through the use of elements blocking parts of thelight before entering the profile sensor. Those blocking elements couldbe LCD based, mechanical based, or based on a multitude of othersolutions readily understood by one skilled in the art.

Simulating a Profile Sensor Using a Traditional Image Sensor

It is possible to utilize a traditional image sensor which includes amatrix of pixels to simulate a profile sensor, as discussed previously.To achieve this, hardware or software may perform mathematicaloperations (such as calculating the average intensity level along a lineon the sensor or the sum of all intensity levels along a line on thesensor) to provide output similar to that of a profile sensor.Typically, this would equate to outputting rows or columns from thetraditional sensor. However, it is possible to output any configurationof pixels, for example a diagonal line. By using this simulated system,it is possible to perform more operations than just the traditional meanand sum of all pixel values on a line, such as masking as previouslydescribed. Furthermore, it would be possible to mask detected light fromareas of a captured image (pixels in the image sensor) known to notcontain any glints. By performing this masking function, the signal tonoise ratio may be increased. An example of an area to mask is the areaoutside of a user's cornea, as this area cannot contribute a glint.

The masking of light from areas of an image not contributing a glint maybe performed using a traditional profile sensor. Further options formasking light include utilizing illuminators whose light may bespatially controlled, such as an infrared OLED array behind a lens, anyarrangement with a DLP or LCOS projector, or any other solution readilyunderstood by a person skilled in the art. Another option is to blocklight from non-contributing areas from reaching the sensor, this may beachieved by a mechanical solution, LCD solution, or any other solutionunderstood by a person skilled in the art. A mechanical LCD solution mayinclude placing a transparent LCD in front of a profile sensor.

Eye Tracker Synchronized with Display

For certain applications of eye tracking it is valuable to synchronizethe eye tracking device with the display, particularly in a wearabledevice. In accordance with this aspect of embodiments of the presentinvention, a wearable device is provided with a display, at least onecamera, and at least one illuminator. The camera(s) and illuminator(s)form an eye tracking device. Either the camera(s) and/or theilluminator(s) may be synchronized with the display. Synchronizing maybe characterized as synchronizing the camera strobe rate with the v-syncof the display.

It is further desirable to synchronize the eye tracking device with aposition device or devices. For example the eye tracking device may besynchronized with an inertial measurement unit or the like, or with aroom position device which uses infrared or other non-visible light.Such a system has been proposed by Valve® under the name “Lighthouse”. Aperson of skill in the art will readily understand how suchsynchronization may function.

Removable Eye Tracker

In accordance with another aspect of embodiments of the presentinvention, a removable eye tracker is provided whereby the eye trackermay be inserted into a wearable device. The eye tracker may then beintegrated with another device such as a phone, tablet, watch, displayor the like.

The eye tracker may include at least one camera and at least oneilluminator, and its primary function may be to track a user's gazerelative to the device into which it is integrated, for example, aphone, tablet, or watch. As a secondary function, the device into whichthe eye tracker is sometimes integrated may be inserted into a wearabledevice. The device may then provide the wearable device withfunctionality such as a display, and the eye tracker may be used todetermine the gaze direction of a wearer of the wearable device. Themethod of operation of the eye tracker may be any traditional method orany method described herein.

Smile Authentication

According to one aspect of the present invention an image sensor in awearable device used for eye tracking may also be used to capture imagesof an area around a user's eyes. For example, these images may beanalyzed to determine if a user is smiling, and whether that smile isgenuine or fake. Characteristics of the areas around a user's eyes maybe used to determine if a smile is fake or genuine. See, for example,Littlewort-Ford, Gwen, Marian Stewart Bartlett, and Javier R. Movellan,“Are your eyes smiling? Detecting Genuine Smiles with Support VectorMachines and Gabor Wavelets,” Proceedings of the 8th Joint Symposium onNeural Computation, 2001. The entire disclosure of the aforementionedpublication is hereby incorporated by reference, for all purposes, as iffully set forth herein.

According to embodiments of the present invention, an image sensor usedfor eye tracking captures at least a portion of the area around the eyeswhen capturing images of the eyes, these images may then be analysedusing known smile or other detection algorithms to determine whether auser's smile or other facial feature is fake or genuine.

Calibration Based on Iris Identification

According to embodiments of the present invention, an image sensor usedfor eye tracking further captures information relating to a user's iris.This iris information can be used to determine the identity of the userfor input into a system connected to the eye tracker.

For example, according to some embodiments of the present invention awearable device is provided wherein at least one image sensor and atleast one infrared illuminator is provided. The image sensor andilluminator faces toward an eye or eyes of a user wearing the device.Optionally, the device further contains a display such as in a VirtualReality display in a wearable headset.

The image sensor captures images of the iris of the user and passes saidimages to a processing device, the processing device may be located onthe wearable device or may be located remote from the processing device,in which case communication may be effected by wired or wireless meansas would be understood by one of skill in the art.

Iris recognition is a known art and uses mathematicalpattern-recognition techniques to uniquely identify a pattern on oneiris, or both of a irises, of a user for identification orauthentication of the user. In its most basic form, iris recognitionincludes the steps of (1) localization—calculating the inner and outerboundaries of the iris; (2) normalization—normalizing the captured datafor consistency; (3) feature extraction—forming a feature vector offeatures extracted from captured images; and (3) matching—classifyingthe feature vector using thresholding techniques.

Many algorithms have been proposed which allow for iris recognition, seefor example Daugman J. G., High Confidence Visual Recognition of Personsby a Test of Statistical Independence, IEEE Transactions on PatternAnalysis and Machine Intelligence, Volume: 15, No. 1 I, 1993, pp. 1148-1161. The entire disclosure of the aforementioned publication is herebyincorporated by reference, for all purposes, as if fully set forthherein.

Based on images of the user's iris, the processing unit connected (wiredor wirelessly) with the wearable device may use the identification ofthe user to influence its function. For example when using an eyetracker, the processing unit may load a calibration profile whichprovides information specific to a user regarding an offset betweentheir calculated gaze position and actual gaze position. By way ofanother example, the identification may be used to authenticate the useras authorized to operate the wearable device, or operate the processingunit connected thereto.

Eye Torsion Compensation

According to another aspect of embodiments of the present invention, itis possible to track eye torsion. By way of explanation, the human eyeis attached to muscles in such a way that the eye, in addition to movingleft/right and up/down, can also rotate such that the top of the irismay be rotated closer to the nose while the bottom of the iris rotatesfurther away from the nose. The opposite rotation is also possible. Thistype of rotation is generally referred to as eye torsion.

When a human rotates their head slightly to their side, most humansautomatically rotate their eyes slightly in the opposite direction,keeping their eyes close to level with the horizon. This effect is onlyin action during small rotations, since it's not possible to rotate theeye a large number of degrees in this way.

This phenomena introduces an additional source of errors in eye trackingsystems for all persons whose fovea isn't perfectly centered along theoptical axis of the eye.

The present invention may track eye torsion by watching the iris and/orother features on the eye ball and/or using orientation information fromthe eye tracker. This may provide the eye tracker with a betterestimation of the position of the fovea, and hence would provide abetter estimate of the gaze of the eye-tracked subject when their headis tilted.

Corneal Curvature

According to one embodiment of embodiments the present invention, the atleast one image sensor captures images of a user's eye. The computingunit utilizes this information to determine the shape of the cornea of auser. Depending on the position and orientation of reflections from aninfrared light source, the curvature of a cornea may be measured. Insome people, their cornea has an abnormal curvature. This may bereferred to as astigmatism.

By using information obtained from an image sensor and infrared lightsources, the curvature of the cornea may be modeled and thus a user withan abnormally shaped cornea may be identified. By determining the shapeof the cornea, corrective measures such as prescribing an appropriatelens may be performed.

Power Consumption and Processing Power Reduction

In some embodiments, to further reduce power consumption of a wearabledevice which may include a virtual reality display or other displaysystem, an eye tracking device may only directly track a gaze positionof a first eye of the user. The gaze position of the user's second eyemay then be determined by a prediction which is based at least in parton the gaze position directly determined for the first eye.

This may be accomplished based on an assumption that the second eye isapproximately on the same horizontal level of the first eye, as isbiologically typical in human beings. In this manner, the power thatwould otherwise be used by an additional eye tracking device (includingilluminators, image sensors, and/or processing power), may be saved. Insome embodiments, the combined determined and predicted gaze positionsof both eyes may then be used to determine a region for foveatedrendering on a display of the wearable device, providing further powersavings due to increase efficiency in video rendering.

In some embodiments, particular software such as gaming and/or otherhigh-end graphical applications may request gaze data from the eyetracking device to inform the application of how to possibly interactwith the user in the future, how much graphical information to provide agraphics processing unit, and/or other purpose. While in otherembodiments all gaze direction information may be passed on to suchapplications, allowing individual applications to request suchinformation, and only providing such information on request, may resultin power and processing savings.

Virtual Reality Panning and Centering

In some embodiments, solutions are provided for easing the ability of auser to pan, and thereafter center, a virtual reality display or otherdisplay system in a user wearable device. Typically, because a virtualreality display is infinite in any direction (i.e., a user looking tothe right in a virtual display will eventually turn 360 degrees to viewthe original scene), panning can become awkward for the user becausethey can only turn their head so much before it is uncomfortable for theuser to continue turning their head.

In order to alleviate this issue, systems described herein may allow fora user to pan a view on the virtual reality display by turning theirhead and moving their gaze location toward a given direction in whichpanning will occur, but allow the displayed scene to be re-centeredabout a point when it is determined that, while the user's head hasremains rotated, the gaze direction of the user has re-centered on thescene (i.e., their gaze location is no longer panning).

In some embodiments, re-centering of the gaze direction must occur forat least a predefined period of time to ensure that the user is indeeddone panning their view. For example, the user's gaze must return to arelatively central region of the current view. The size, shape, andposition of the region may, in some embodiments, be set by the user. Insome embodiments, the region may be visible in different manners,potentially as set by the user (i.e., a lightly colored indication ofthe region may be overlaid onto other content on the display). In someembodiments, an indication (i.e., audible or visual cue) may be providedto the user to confirm that the virtual display view has beenre-centered, and they may again move their head position to astraightforward, central, neutral position. This re-centering of theuser's head may be allowed by the system without causing the display tobe re-panned in the opposite direction of the original panning.

Similarly, if a user's gaze direction is also in the same direction astheir head movement, or within a certain/predefined angular direction ofeach other, panning speed may start and/or be increased over situationswhere the user's head remains straightforward (i.e., where panning wouldstop and/or be decreased in speed), but their gaze direction indicates apan is desired (i.e., by moving of the gaze direction to the peripheralview edges). Additionally, panning speed could be dependent on, and/ordirectly proportional to, the magnitude of the user's head movement.That meaning that large or sudden movements of the user's head couldincrease pan speed quickly, while small or slow movements of the user'shead could increase pan speed slowly.

Thus, in one embodiment systems and methods for panning (andre-centering) content on a display of a wearable device may be provided.As shown in FIG. 5, the systems described herein may perform a method500 which includes at block 510, determining, via an eye trackingdevice, a gaze direction of a user of a wearable device. The method mayalso include at block 520, determining, via a movement detection system,a head direction of the user of the wearable device. The movementdetection system may include any internal/integrated or external/remotedevice to determine the head position of the user. The movementdetection system may determine head position through any means now know,or later known, in the art.

The method may also include at block 530, based at least in part on thegaze direction and the head direction both being consistent with aparticular direction, causing content displayed on a display of thewearable device to be panned in the particular direction. The method mayalso include, at block 540, determining during panning of the content,via the eye tracking device, that the gaze direction of the user hasreturned to a neutral position. The method may also include, based atleast in part on the gaze direction of the user returning to the neutralposition, causing content displayed on the display of the wearabledevice to stop panning.

Additionally, the head direction of the user exceeding a certain angulardirection from a neutral/forward direction may also the panningdirection/speed. Generally, speed of panning may be based on both thegaze and head direction. An additional input may be provided by user toinstruct the system to stop panning. Additionally, in some embodiments,the system may provide a visual and/or audible indication to the userthat panning has stopped, and the user may move their head back to theforward/neutral direction without concern that panning in the reversedirection will occur (as shown at block 550).

Virtual Reality Mapping of Input Devices

In some embodiments, gaze detection may allow for mapping of inputdevice actions onto the surface of a virtual object in a virtual realitydisplay. For example, if a virtual sphere is located in the virtualspace, the eye tracking device may determine that at some point theuser's gaze direction is toward the sphere. Upon receipt of a secondaryinput, or the expiration of a predefined period of time, associatedinput devices may have their controls mapped to the virtual object.

The secondary input could include a contact input from a traditionalinput device such as a keyboard, touch pad (or other touch sensitivedevice), mouse, or trackball; or could also include a non-contact inputsuch as a voice command or gaze input. More specifically, a contactinput may have directional input on the touch sensitive surfacecontrolling the mapping onto the virtual sphere to a user designatedposition; wherein the direction input means touch gesture; and thecontact input may also pressure signal received from a pressuresensitive device associated with the touch sensitive surface; last butnot least, the contact input can be combined with pressure touch andtouch gesture. A proximity input may also be possible where theproximity touch input is received from touch sensitive device associatedwith a proximity sensor without physical contact with the touchsensitive surface.

Mapping control of an input device to the object may take many forms.For example, if a mouse is the input device being mapped, input from themouse may determine a rotation of the object in virtual space, or maycause a visual indicator, such as a pointer, on the object to be movedabout the virtual object. This may allow for complex actions to beexecuted by the user using the virtual object.

In another example, a virtual control panel having many virtual inputssuch as switches and knobs may be present in the virtual realitydisplay. Upon determining that the gaze direction of the user isdirected to the virtual control panel, and that either a predefinedperiod of time has passed or a secondary input has been received,controls of a keyboard or mouse may be mapped to the control panel. Thismay allow keys of the keyboard to be correspondingly mapped to thecontrol panel, or mouse movement to cause a visual indicator or pointer(i.e., a visual representation of the user's hand) to be moved acrossthe control panel to select or activate various virtual inputs thereon.

In some embodiments, a predefined portion of the virtual control panel(or other virtual object) may be the area in which the user's gazedirection must lie to activate control mapping (rather than the user'sgaze direction being located anywhere on the control panel). In someembodiments, the predefined portion may be visually indicated and/orlabeled in the virtual display.

Thus, in some embodiments, systems which perform the methods discussedherein may be provided. In one example shown in FIG. 6, a method 600 formapping an input device to a virtual object in virtual space displayedon a display device may include, at block 610, determining, via an eyetracking device, a gaze direction of a user.

The method may also include, at block 620, based at least in part on thegaze direction being directed to a virtual object in virtual spacedisplayed on a display device, modifying an action to be taken by one ormore processors in response to receiving a first input from an inputdevice. This may also occur in response to the gaze direction beingdirected to the virtual object for at least a predefined period of time,or while a secondary input is received. The user may also be notified byvisible/audible indication that the potential action has been modified.

Modification of the action may include modifying the action from anormal action to be taken in response to receipt of the first input to aspecialized action in the virtual space associated with the virtualobject. The specialized action in the virtual space associated with thevirtual objection may be causing the first input to rotate the virtualobject and/or cause the first input to move the virtual object. In theseor other embodiments, the specialized action in the virtual spaceassociated with the virtual object may be causing the first input tomove a secondary object about the surface of the virtual object. Thesecondary object may move in a direction corresponding to a directionassociated with the first input, and may be a pointer or other virtuallocation marker.

The method may also include, thereafter, in response to receiving theinput from the input device, at block 630, causing the action to occurat block 640, wherein the action correlates the first input to aninteraction with the virtual object.

In response to some input of a user, perhaps a tertiary or other input,after a certain amount of time has passed, or because their gaze hasmoved away from the virtual object in question, mapping of the input tothe virtual object may cease, as shown at block 650.

Merely by way of example, input devices which could be mapped include, atouch sensitive device, a touch sensitive screen, a pressure sensitivedevice, a mouse, a trackball, a joystick, a handheld controller, astylus, a keyboard, a speech input device, and/or any other input devicediscussed herein or known in the art.

In some embodiments, the apparent effect of an input device mapped to avirtual object as described herein may be magnified or de-magnified, aswill be perceived by the user upon operation. Merely by way of example,in an embodiment where a user is rotating a virtual representation of aplanet, a very small movement input of a mouse which is mapped to thatvirtual object may cause a large degree of spin of the virtual planet.Conversely, where a user is rotating a virtual representation of amolecule, a very large input of a mouse which is mapped to that virtualobject may only cause a small degree of spin of the virtual molecule.The amount of magnification or de-magnification may depend on anotherinput as set by the user, or may be pre-programmed into the particularapplication. The magnification or de-magnification may also be variabledepending on various user and program set variables.

Saccade Predicted Areas of Interest in a Display

In some embodiments, saccades by a user's eye(s) may be detected, andused to estimate or determine where the user's gaze direction will lieupon completion of the saccade. Additionally, saccades for differentindividual users can be analyzed, and information related theretostored, to predict future changes in gaze direction for a particularuser upon occurrence of saccades thereby (i.e., saccades of differentspeeds for different users result in different angular changes of gazedirection).

Furthermore, known salient regions or objects of interest may alsoinform any prediction algorithm of the likelihood that a user's gazedirection will eventually lie thereon upon completion of a saccade inthe direction of the region or object. The gaze direction patterns of auser, including the lengths of time a user's gaze direction lies on agiven region or object, may also be analyzed to determine whether suchregions or objects are particularly salient for when they are displayedin the future.

Consequently, the above information regarding user saccades and gazedirection changes, whether in the direction of known or unknown salientregions or objects, may be used to implement foveated rendering. Forexample, if a known salient region or object is to be displayed in thevirtual display, and upon display of the region or object, the user'seye(s) saccade toward the region or object, the region or object may berendered in greater quality prior to the user's gaze direction arrivingthereon.

Even when the saliency of a region or object is unknown when displayed,or when no particularly salient region or object is being displayed, anangular change in gaze direction, and corresponding likely resultingviewing region, may be determined or estimated by detecting a saccade isoccurring. The determined or estimated amount of angular change in gazedirection may be particular to the user based on previous recordedsaccade data therefor, or may be default data applicable to all users,perhaps prior to recorded data for a particular user is available.

In some embodiments, if saccade information does not allow for precisedetermination of the user's likely resulting gaze direction, multipleknown salient regions or objects which are located at the most likelygaze directions may be rendered in greater quality. In some embodiments,the increase in rendering quality for each region or object may beproportional to the likelihood that the user's gaze direction mayeventually lie thereon. For example, if two regions are equally likelyto be the resultant gaze area of a user's saccade, rendering quality forboth regions may be increased similarly. However, if one region is themore likely resultant gaze area, then its rendering quality may beimproved to a greater degree than the less likely resultant gaze area.

The way in which the image displayed on display device 110 may bemodified by graphics processing device may vary depending on theembodiment, but regardless, the way in which the image is displayed maybe intended to increase the image quality of portions of the image onwhich a user's gaze, or focused gaze, is directed, relative to thoseportions of the image to which the user's gaze, or focused gaze, is notdirected. In this manner, the use of available resources of graphicsprocessing device, and/or other system resources, are maximized todeliver image quality where it matters most on display device 110. Todemonstrate, FIG. 9 illustrates a display device 110 showing a user'sgaze point 910 and an area 920 around user's gaze point 910 in whichembodiments of the invention may increase the quality of the imagerelative to the remaining area 930 of the display device 110. Thus, invarious embodiments of the invention, the quality of the image producedacross display device 110 may be increased in area 920 relative toremaining area 930.

When “modification” of an image presented on display device 110 isdiscussed herein, it shall be understood that what is intended is that asubsequent image displayed on display device 110, is different than aprior image displayed on display device 110. Thus, graphics processingdevice and display device 110, or other device(s) discussed herein,“modify” an image by causing a first image to be displayed and then asecond image to be displayed which is different than the first image.Any other change of an image discussed herein, for example, increasingor decreasing of image quality, shall also be understood to mean that asubsequent image is different than a prior image. Note that a change ormodification of an image may include changing or modifying only aportion of the image. Thus, some portions of a prior image may be thesame as a subsequent image, while other portions may be different. Inother situations, the entirety of a prior image may be different than asubsequent image. It shall be understood that the modification of anarea or an entirety of an image does not necessarily mean every finiteportion of the area or entirety are changed (for example, each pixel),but rather that the area or entirety may be changed in some potentiallyconsistent, predefined, or ordered manner (for example, the quality ofthe image is changed).

Increasing the quality of the image may include increasing the qualityof any one or more of the below non-exclusive list of graphicalcharacteristics, in addition to other possible characteristics known inthe art:

-   -   Resolution: The number of distinct pixels that may be displayed        in one or more dimensions. For example, “1024×768” means 1024        pixels displayed in height and 768 pixels displayed in width.    -   Shading: Variation of the color and brightness of graphical        objects dependent on the artificial lighting projected by light        sources emulated by graphics processing device 130.    -   Texture-mapping: The mapping of graphical images or “textures”        onto graphical objects to provide the objects with a particular        look. The resolution of the textures influence the quality of        the graphical object to which they are applied.    -   Bump-mapping: Simulation of small-scale bumps and rough        gradients on surfaces of graphical objects.    -   Fogging/participating medium: The dimming of light when passing        through non-clear atmosphere or air.    -   Shadows: Emulation of obstruction of light.    -   Soft shadows: Variance in shadowing and darkness caused by        partially obscured light sources.    -   Reflection: Representations of mirror-like or high gloss        reflective surfaces.    -   Transparency/opacity (optical or graphic): Sharp transmission of        light through solid objects.    -   Translucency: Highly scattered transmission of light through        solid objects.    -   Refraction: Bending of light associated with transparency.    -   Diffraction: Bending, spreading and interference of light        passing by an object or aperture that disrupts the light ray.    -   Indirect illumination: Surfaces illuminated by light reflected        off other surfaces, rather than directly from a light source        (also known as global illumination).    -   Caustics (a form of indirect illumination): Reflection of light        off a shiny object, or focusing of light through a transparent        object, to produce bright highlights on another object.    -   Anti-aliasing: The process of blending the edge of a displayed        object to reduce the appearance of sharpness or jagged lines.        Typically an algorithm is used that samples colors around the        edge of the displayed object in to blend the edge to its        surroundings.    -   Frame rate: For an animated image, the number of individual        frames presented during a certain period of time to render        movement within the image.    -   3D: Visual and temporal characteristics of an image which cause        the image to appear to be three dimensional to a viewer.

The size and shape of the area of the image which may be modified toappear in greater quality can vary depending on the embodiment. Merelyby way of example, the shape of the area may be circular, oval, square,rectangular, or polygonal. In some embodiments, the quality of the imagewithin the area may be uniformly increased. In other embodiments, theincrease in quality of the image may be greatest at the center of thearea (i.e., proximate to the gaze point), and decrease towards the edgesof the area (i.e., distal to the gaze point), perhaps to match thequality of the image surrounding the area. To demonstrate, FIG. 10Ashows how image quality may decrease in a linear or non-liner continuousmanner from the center of a gaze area outward, while FIG. 10B shows howimage quality may decrease in a stepped manner from the center of a gazearea outward.

In some embodiments, modifying the image displayed on display device 110may occur in response to the detection of a change in the gaze point.This may occur in a number of fashions, some of which are describedbelow.

In some embodiments, an entirety of the image may be modified during theperiod of change in the gaze point of the user, and once the change inthe gaze point of the user ceases, either the area around end gaze pointof the user or a remainder of the image (portions of the image notaround the end gaze point) may be modified. Merely by way of example, inone embodiment, the quality of the entire image may be increased duringmovement of the user's gaze (sometimes referred to as a saccade), butthe increase in quality may only be sustained in an area around theuser's end gaze point once the saccade is complete (i.e., the quality ofthe remainder of the image may be decreased upon completion of thesaccade). In a different embodiment, the quality of the entire image maybe decreased during a saccade, but the decrease in quality may only besustained areas besides around the user's end gaze point once thesaccade is complete (i.e., the quality of the area of the image aroundthe user's end gaze point may be increased upon completion of thesaccade).

Additionally, the use of other system resources, including for example,processor/computer and related resources, may also be modified during auser's saccade. For example, non-graphical operations may besupplemented by the resources of processor/computer and graphicsprocessing device, during a saccade. More specifically, during asaccade, non-graphical calculations necessary for other systemoperations may proceed at greater speed or efficiency because additionalresources associated with processor/computer and graphics processingdevice are made available for such operations.

In some embodiments, modifying the image displayed on display device 110may include modifying a portion of the image in an area around ananticipated gaze point of the user, potentially by increasing thequality thereof. The anticipated gaze point may be determined based onthe change in the gaze point of the user. To determine the anticipatedgaze point of a user, eye tracking device and/or another processor (i.e,the computer or game consoler's processor), may determine a rate of thechange in the gaze point of the user on display device, and determinethe anticipated gaze point based at least in part on this rate of thechange.

The rate of change of the gaze point of the user, also referred to asthe velocity or speed of a saccade by the user is directly dependent onthe total change in the gaze point of the user (often referred to as theamplitude of the saccade). Thus, as the intended amplitude of a user'ssaccade increases, so does the speed of the saccade. While the saccadeof a human user can be as fast as 900°/second in humans, for saccades ofless than or about 60°, the velocity of a saccade is generally linearlyand directly dependent on the amplitude of the saccade. For example, a10° amplitude is associated with a velocity of 300°/second and a 30°amplitude is associated with a velocity of 500°/second. For saccades ofgreater than 60°, the peak velocity starts to plateau toward the maximumvelocity attainable by the eye (900°/second). In response to anunexpected stimulus, a saccade normally takes about 200 milliseconds(ms) to be initiated and then lasts from about 20 to about 200 ms. Basedon these relationships between saccade speed and amplitude, embodimentsof the invention may determine anticipated gaze points based on saccadevelocity. Other predetermined models of mathematical relationshipsbetween saccade speed and amplitude may also be employed by variousembodiments of the invention to determine an anticipated gaze point.

In some embodiments, the portion of the image modified around theanticipated gaze point may also include the portion of the image aroundthe original gaze point (i.e., the gaze point from which the user'ssaccade started). While the shape of the portion of the image modifiedmay be any of those shapes described above, in some embodiments it maybe a triangle or a trapezoidal shape having a progressively greaterwidth perpendicular to a direction of the saccade as shown in FIG. 11.

In FIG. 11, display device 110 is shown, and an initial user gaze point1110 is shown thereon. Prior to any change in initial gaze point 1110,embodiments of the invention may provide increased graphics quality inarea 1120. When a user saccade, represented by arrow 1130, is detectedby eye tracking device, the size and shape of area 1120 may change toaccommodate both initial gaze point 1110 and anticipated gaze point1140. The changed area 1150, while being triangular and/or trapezoidalin this embodiment, may be shaped and sized differently in otherembodiments. Merely by way of example, an entire side of display device110 from the initial gaze point to the edges of the display in thedirection of the saccade may also be included in changed area 1150 toaccount for more possibilities of where the user's gaze point may end.In other embodiments, a circular, oval, or square changed area 1150 maybe provided. In yet other embodiments, changed area 1150 may includeseparate and distinct areas around the initial gaze point 1110 andanticipated gaze point 1140.

In some embodiments, the size or shape of the area around the gaze pointfor which an image is modified (or which remains unmodified from aheightened quality in various embodiments), is dynamic. This may occurbased at least in part on any number of factors, including the currentlocation of the gaze point relative to the image or display device.Merely by way of example, if a user moves their gaze point to a certainportion of the screen, a predefined portion of the screen may bemodified via increased quality therein (for example, a corner portion ofthe display having a map of a virtual area in a video game). In someembodiments, if enough user saccades having one or more predefinedcharacteristics are detected in predefined amount of time, the entiretyof the display may be modified to be rendered in greater quality.

In another embodiment of the invention, a non-transitory computerreadable medium having instructions thereon for presenting graphics ondisplay device 110 is provided. The instructions may be executable byone or more processors to at least display an image on display device110. The instructions may also be executable to receive information fromeye tracking device indicative of at least one of a gaze point of a useron display device 110, or a change in the gaze point of the user ondisplay device 110. The instructions may further be executable to causegraphics processing device to modify the image displayed on displaydevice 110 based at least in part on the gaze point of the user ondisplay device 110, or the change in the gaze point of the user ondisplay device 110. Thus, a non-transitory computer readable medium ableto implement any of the features described herein in relation to otherembodiments is also provided.

In another embodiment of the invention, a method 1200 for presentinggraphics on display device 110 is provided as shown in FIG. 12. At step1210, method 1200 may include displaying an image on display device 110.At step 1220, method 1200 may also include receiving information fromeye tracking device indicative of at least one of a gaze point of a useron display device 110, or a change in the gaze point of the user ondisplay device 110. At step 1230, method 1200 may further includecausing graphics processing device to modify the image displayed ondisplay device 110 based at least in part on the gaze point of the useron display device 110, or the change in the gaze point of the user ondisplay device 110. Step 1230 may include, at step 1233, increasing thequality of the image in an area around the gaze point of the user,relative to outside the area. Step 1230 may also include, at step 1236,decreasing the quality of the image outside an area around the gazepoint of the user, relative to inside the area. Thus, a method toimplement any of the features described herein in relation to otherembodiments is also provided.

In some embodiments, the systems and methods described herein may betoggled on and off by a user, possibly to account for multipleadditional viewers of display device 110 being present. In otherembodiments, the systems and methods described herein may automaticallytoggle on when only one user is viewing display device 110 (as detectedby eye tracking device), and off when more than one user is viewingdisplay device 110 (as detected by eye tracking device). Additionally,in some embodiments, the systems and methods described herein may allowfor reduction in rendering quality of an entire display device 110 whenno viewers are detected, thereby saving system resources and powerconsumption when display device 110 is not the primary focus of anyviewer.

In other embodiments, the systems and methods described herein may allowfor modifying multiple portions of an image on display device 110 toaccount for multiple viewers as detected by eye tracking device. Forexample, if two different users are focused on different portions ofdisplay device 110, the two different areas of the image focused on maybe rendered in higher quality to provide enhanced viewing for eachviewer.

In yet other embodiments, data associated with an image may inform thesystems and methods described herein to allow prediction of which areasof an image may likely be focused on next by the user. This data maysupplement data provided by eye tracking device to allow for quicker andmore fluid adjustment of the quality of the image in areas likely to befocused on by a user. For example, during viewing of a sporting event, apicture-in-picture of an interview with a coach or player may bepresented in a corner of the image. Metadata associated with the imagefeed may inform the systems and methods described herein of the likelyimportance, and hence viewer interest and likely focus, in thesub-portion of the image.

Trajectory Adjustment of Projectiles in Virtual Reality

In virtual reality embodiments, when virtual objects are thrown orotherwise launched by user action, a problem exists whereby the usercannot easily estimate the weight of the object and thus how far theobject, now a projectile, will fly when launched. Given that accuratedistances may be necessary to make the virtual interaction usable orsuccessful, gaze detection may serve the purpose of assisting inincreasing in accurate placement of the desired target location for theprojectile.

In some embodiments, eye tracking devices may be used to determine thegaze direction of a user launching a virtual object, and allow for thelocation of the gaze direction on a virtual display to either be used todetermine, or assist in determining, the intended destination of theprojectile. In some embodiments, the exact gaze location on the virtualdisplay may be used as the intended target of the user.

In other embodiments, the gaze location on the virtual display maymerely inform the software process of the intended target, and this mayaffect, to a variable degree depending on the algorithm, the calculatedtarget for a projectile. Thus, while an initial target may be calculatedby the algorithm, and depend on factors such as speed of the throwing orother motion which initiated the launch of the projectile and thevirtually assigned weight of the object, the gaze direction may be used,to variable degrees, as assigned by the algorithm, to modify thecalculated initial target.

Distributed Multi-Camera Array ON/IN VR Lens

In traditional virtual reality or other wearable devices, it can bechallenging to position image sensors and camera associated with an eyetracking device so that they can obtain good imaging, but withoutinterfering with the viewing lens of the display system therein. Inorder to solve this problem, one solution provided by variousembodiments of the invention is to dispose one or more arrays ofminiature cameras/image/light sensors (as well as illuminators asdiscussed herein) on or in the lenses directly in front of the user'seyes. Because the cameras are very small (e.g., 1 mm³) and very close tothe user's eyes, they will essentially appear to be invisible to theuser, as they are not within active focal distance of the user. As shownin FIG. 7A, in front of a display device 110 of a given system, aviewing/primary lens 710 may be present, and an array ofcameras/illuminators 720 may also be present on or in lens 710.Cameras/illuminators 720 are shown larger than to-scale for the purposesof demonstration in this figure. FIG. 7A will be discussed below infurther detail.

While each camera of an array may only have limited resolution, when theimages of all cameras are combined and reconstructed by an associatedprocessing device, standard images may be obtained. Additionally,because an array is used, additional depth information of the image maybe obtained over the use of a single camera or image sensor observingthe eye(s).

User and Obstruction Presence Verification for Safe Light SourceOperation

Consumer device must meet various standards of safety with respect tolight and laser sources near a user's eyes. The closer the user is tothe consumer device light/laser source, the lower the magnitude ofillumination allowed to satisfy the various standards.

In some embodiments, devices herein may include safety mechanismarranged to protect the user and verify that the standards are met. Inone embodiment, the eye tracking devices herein may determine if a useris present in front of the device via image sensors, and reactaccordingly.

If no user is present, illumination levels of the display and/or eyetracking illuminators are lowered to be safe at any distance. Because nouser is present, the display and/or illuminators will be illuminated ata safe level for any condition that arises. However, if a user isdetermined to be present, the distance from any display and/or eyetracking subsystems such as illuminators may be calculated, and themaximum allowable illumination thereof allowed by the system may berestored. In some embodiments, if an eye tracking device determines nouser is present, a display device may be turned off in order to savepower.

In some embodiments, the systems herein may also be able to determine ifany illuminator is obstructed, either by direct detection of theobstruction by an image sensor, or by lack of detection by an imagesensor of light from a particular illuminator. If an illuminator orother light emitting device such as a display is determined to beobstructed, such light producing devices may be dimmed or deactivatedentirely, in order to save power.

Visibility Reduction of Illumination Devices and Image Sensors in VRDevices

In some embodiments, in order to arrange illumination devices and imagesensors of the invention in the most advantageous position, flexibleprinted circuit (FPC) supported illuminators and image sensors may besunk into the lenses of virtual reality or other display devices,perhaps in locations as shown in FIG. 7A. LEDs or other illuminators, aswell as image sensors, may be located on very thin FPCs, and thenorientated so as to minimize the visible profile thereof.

Merely by way of example, illuminators and image sensors may be mountedon FPCs such that the illuminator or image sensor is mounted facing theuser, but only the profile of the FPC (i.e., the thickness of the FPC)is viewed directly by a user of the device. In some embodiments, the FPCmay be attached to the illuminator or image sensor such it couples tomore than one side of the illuminator/sensor. In this manner, capture oflight to or directed from the illuminator/sensor may be improved.

In these and other embodiments, another method may also be used tominimize the appearance of illuminators in a virtual reality or otherdisplay device. In these embodiments, optical fibers may be embeddedinto grooves on the front (user) side of the viewing lens of the device.FIG. 7B shows such a groove 730 and the optical fiber 740 deposited inthe surface of lens 710. The optical fibers may be numerouslydistributed across the front side of the lens so as to generate theillumination necessary for eye tracking. LEDs or other illuminationsources such as luminescent diodes may be coupled to the end of theoptical fibers at the edge, or away from, the lens.

Any void in the grooves where the optic fibers are placed may be filledwith a substance 750 such as glue or other adhesive to maintain theposition of the fiber, and to minimize refraction therein. The substancemay have the same, or similar, refraction index to the lens itself inorder to minimize visible distortion of the lens to the user.

As shown in FIG. 7C, an angled and/or reflected surface 760 within thelens 710 at the termination point 745 of the optical fiber 740 may guidelight from the end of the optical fiber toward the eye. To furtherminimize potentially stray light from the optical fiber within the lens,a light absorptive material 770 may also be disposed near thetermination point of the optical fiber, perhaps behind the angledsurface. A beam shaping material 780 such as epoxy, silicone, or similarsubstance may also be applied to the lens near the termination point toassist in directing light toward the proper location on the user's eye.

Exemplary Computer System

The above is a block diagram illustrating an exemplary computer system800, as shown in FIG. 8, in which any of the embodiments of the presentinvention may be implemented. This example illustrates a computer system800 such as may be used, in whole, in part, or with variousmodifications, to provide the functions of the systems and methodsdescribed above.

The computer system 800 is shown including hardware elements that may beelectrically coupled via a bus 890. The hardware elements may includeone or more central processing units 810, one or more input devices 820(e.g., eye-tracking device, whether integrated or not with anotherdevice; a mouse; a keyboard; a touchpad; a microphone; handheldcontroller; etc.), and one or more output devices 830 (e.g., a displaydevice, a wearable device having a display, a printer, etc.). Thecomputer system 800 may also include one or more storage device 840. Byway of example, storage device(s) 840 may be transitory and/ornon-transitory disk drives, optical storage devices, solid-state storagedevice such as a random access memory (“RAM”) and/or a read-only memory(“ROM”), which can be programmable, flash-updateable and/or the like.

The computer system 800 may additionally include a computer-readablestorage media reader 850, a communications system 860 (e.g., a modem, anetwork card (wireless or wired), an infra-red communication device,Bluetooth™ device, cellular communication device, etc.), and workingmemory 880, which may include RAM and ROM devices as described above. Insome embodiments, the computer system 800 may also include a processingacceleration unit 870, which can include a digital signal processor, aspecial-purpose processor and/or the like.

The computer-readable storage media reader 850 can further be connectedto a computer-readable storage medium, together (and, optionally, incombination with storage device(s) 840) comprehensively representingremote, local, fixed, and/or removable storage devices plus storagemedia for temporarily and/or more permanently containingcomputer-readable information. The communications system 860 may permitdata to be exchanged with a network, system, computer and/or othercomponent described above.

The computer system 800 may also include software elements, shown asbeing currently located within a working memory 880, including anoperating system 884 and/or other code 878. It should be appreciatedthat alternate embodiments of a computer system 800 may have numerousvariations from that described above. For example, customized hardwaremight also be used and/or particular elements might be implemented inhardware, software (including portable software, such as applets), orboth. Furthermore, connection to other computing devices such as networkinput/output and data acquisition devices may also occur.

Software of computer system 800 may include code 878 for implementingany or all of the function of the various elements of the architectureas described herein. For example, software, stored on and/or executed bya computer system such as system 800, can provide the functions of themethods and systems discussed above. Methods implementable by softwareon some of these components have been discussed above in more detail.

The invention has now been described in detail for the purposes ofclarity and understanding. However, it will be appreciated that certainchanges and modifications may be practiced within the scope of theappended claims.

What is claimed is:
 1. A system for determining a gaze direction of auser, wherein the system comprises: a first illuminator configured toilluminate an eye of a user; a first profile sensor configured to detectlight reflected by the eye of the user; and at least one processorconfigured to determine a gaze direction of the user based at least inpart on light detected by the first profile sensor.
 2. The system fordetermining a gaze direction of a user of claim 1, wherein the systemfurther comprises: a second profile sensor configured to detect lightreflected by the eye of the user, wherein determining the gaze directionof the user is further based at least in part on light detected by thesecond profile sensor.
 3. The system for determining a gaze direction ofa user of claim 2, wherein the at least one processor is furtherconfigured to: determine a location of a cornea center of the eye basedat least in part on light detected by the first profile sensor and lightdetected by the second profile sensor.
 4. The system for determining agaze direction of a user of claim 1, wherein the first profile sensor isconfigured to: detect light in two dimensions.
 5. The system fordetermining a gaze direction of a user of claim 2, wherein: the firstprofile sensor is configured to detect light in one dimension; and thesecond profile sensor is configured to detect light in one dimension. 6.The system for determining a gaze direction of a user of claim 5,wherein: the first profile sensor is orientated orthogonally to thesecond profile sensor.
 7. The system for determining a gaze direction ofa user of claim 5, wherein the system further comprises: a firstcylindrical lens between the first profile sensor and the eye; and asecond cylindrical lens between the second profile sensor and the eye.8. The system for determining a gaze direction of a user of claim 1,wherein the system further comprises: a second illuminator configured toilluminate the eye of the user.
 9. The system for determining a gazedirection of a user of claim 8, wherein the at least one processor isfurther configured to: modulate activation of the first illuminator andthe second illuminator such that only the first illuminator or thesecond illuminator is activated at a particular point in time.
 10. Thesystem for determining a gaze direction of a user of claim 1, whereindetermining the gaze direction of the user based at least in part onlight detected by the first profile sensor comprises: determining alocation of a glint on the eye caused by light reflected by the eye ofthe user, based at least in part on a higher magnitude light leveldetected at one or more pixels of the profile sensor.
 11. The system fordetermining a gaze direction of a user of claim 10, wherein determiningthe gaze direction of the user based at least in part on light detectedby the first profile sensor further comprises: identifying a subset of atotal number of pixels of the profile sensor which include and surroundthe one or more pixels of the profile sensor which detected the highermagnitude light level; and analyzing only the subset of the total numberof pixels of the profile sensor during a subsequent determination ofgaze direction.
 12. The system for determining a gaze direction of auser of claim 1, wherein: the system further comprises an area imagesensor configured to detect light reflected by the eye of the user; anddetermining the gaze direction of the user is further based at least inpart on light detected by the area image sensor.
 13. The system fordetermining a gaze direction of a user of claim 12, wherein: the areaimage sensor operates at between about 0.5 and about 10.0 hertz.
 14. Thesystem for determining a gaze direction of a user of claim 12, wherein:the area image sensor has a sensitive area having a total number ofpixels characterized by a total number of rows and a total number ofcolumns; and determining the gaze direction of the user based at leastin part on light detected by the area image sensor comprises:determining magnitudes of light exposure at a subset of the total numberof rows during one or more illumination periods; determining magnitudesof light exposure at a subset of the total number of columns during oneor more illumination periods; identifying a subset of the total numberof pixels based on the magnitudes of light exposure at the subset of thetotal number of rows and the magnitudes of light exposure at the subsetof the total number of columns; and analyzing only the subset of thetotal number of pixels of the area image sensor during a subsequentillumination period.
 15. The system for determining a gaze direction ofa user of claim 12, wherein: the area image sensor has a sensitive areahaving a total number of pixels characterized by a total number of rowsand a total number of columns; and determining the gaze direction of theuser based at least in part on light detected by the area image sensorcomprises: determining magnitudes of light exposure at a subset ofpixels in each of the total number of rows during one or moreillumination periods; determining magnitudes of light exposure at asubset of pixels in each of the total number of columns during one ormore illumination periods; identifying a subset of the total number ofpixels based on the magnitudes of light exposure at the subset of pixelsin each of the total number of rows and the magnitudes of light exposureat the subset of pixels in each of the total number of columns; andanalyzing only the subset of the total number of pixels of the areaimage sensor during a subsequent illumination period.
 16. The system fordetermining a gaze direction of a user of claim 1, wherein: at least thefirst illuminator and the first profile sensor are disposed within awearable device.
 17. The system for determining a gaze direction of auser of claim 16, wherein the wearable device comprises: a displaydevice; and a cold mirror on a back side of the display device, wherein:the first illuminator comprises a near-infrared illuminator; the coldmirror is configured to reflect visible light toward a front side of thedisplay device, and allow near-infrared to pass through the cold mirror;and the first profile sensor is disposed on the opposite side of thecold mirror from the display device.
 18. The system for determining agaze direction of a user of claim 17, wherein: the wearable devicefurther comprises a lens in front of the display device; and the atleast one processor is further configured to compensate for the presenceof the lens before or during determining the gaze direction of the user.19. A method for determining a gaze direction of a user, wherein themethod comprises: illuminating an eye of a user; detecting, with aprofile sensor, light reflected by the eye of the user; and determining,with at least one processor, a gaze direction of the user based at leastin part on light detected by the profile sensor.
 20. A non-transitorymachine readable medium having instructions stored thereon fordetermining a gaze direction of a user, wherein the instructions areexecutable by one or more processors to at least: cause an illuminatorto illuminate an eye of a user; detect, with a profile sensor, lightreflected by the eye of the user; and determine a gaze direction of theuser based at least in part on light detected by the profile sensor. 21.A system for determining a gaze direction of a user, wherein the systemcomprises: a first illuminator configured to illuminate an eye of auser; an area image sensor configured to detect light reflected by theeye of the user; and at least one processor configured to determine agaze direction of the user based at least in part on light detected bythe area image sensor.
 22. The system for determining a gaze directionof a user of claim 21, wherein: the area image sensor has a sensitivearea having a total number of pixels characterized by a total number ofrows and a total number of columns; and determining the gaze directionof the user based at least in part on light detected by the area imagesensor comprises: determining magnitudes of light exposure at a subsetof the total number of rows during one or more illumination periods;determining magnitudes of light exposure at a subset of the total numberof columns during one or more illumination periods; identifying a subsetof the total number of pixels based on the magnitudes of light exposureat the subset of the total number of rows and the magnitudes of lightexposure at the subset of the total number of columns; and analyzingonly the subset of the total number of pixels of the area image sensorduring a subsequent illumination period.
 23. The system for determininga gaze direction of a user of claim 21, wherein: the area image sensorhas a sensitive area having a total number of pixels characterized by atotal number of rows and a total number of columns; and determining thegaze direction of the user based at least in part on light detected bythe area image sensor comprises: determining magnitudes of lightexposure at a subset of pixels in each of the total number of rowsduring one or more illumination periods; determining magnitudes of lightexposure at a subset of pixels in each of the total number of columnsduring one or more illumination periods; identifying a subset of thetotal number of pixels based on the magnitudes of light exposure at thesubset of pixels in each of the total number of rows and the magnitudesof light exposure at the subset of pixels in each of the total number ofcolumns; and analyzing only the subset of the total number of pixels ofthe area image sensor during a subsequent illumination period.
 24. Thesystem of claim 21, wherein the system further comprises: a Fresnel lensin front of a display device; a hot mirror on at least one side of theFresnel lens or the display device; and wherein: the at least oneprocessor is further configured to adjust the trajectory of virtualmissiles which are caused to be virtually propelled by the user invirtual space; and the first illuminator and image sensor are reversiblycoupled with the system so that they may be used in other devices.